HFC0400 Fixed Frequency Flyback Controller SOIC8

HFC0400 Fixed Frequency Flyback Controller SOIC8

HFC0400 is a fixed-frequency current-mode controller with built-in slope compensation.

Key Specifications

Features

• Fixed-frequency current-mode control with built-in slope compensation
• Frequency foldback down to 25kHz at light loads
• Burst mode for low standby power consumption
• Frequency jitter to reduce EMI signature
• X-cap discharge function
• Internal high-voltage current source
• VCC under-voltage lockout with hysteresis (UVLO)
• Brown-out protection on HV pin
• Overload protection with programmable delay
• Thermal shutdown (auto-restart with hysteresis)

Typical Application Circuit

Applications

• AC/DC adapters for notebook computers, tablets, and smartphones
• Offline battery chargers

Design Notes

• The PFC inductor must support the maximum duty cycle at the lowest line voltage, which is where saturation risk peaks.
• High-voltage startup and X-capacitor discharge paths dominate no-load standby loss; verify them against the efficiency target.
• Leakage inductance and the RCD clamp set the turn-off loss — snubber values are a thermal trade-off, not a fixed recipe.
• Synchronous rectification timing must track the primary switching; a mistimed SR FET conducts through its body diode and fails hot.

Common Questions